The Prospective Investigation of Pulmonary Embolism Diagnosis III (PIOPED-III) is a multicenter prospective investigation designed to determine the diagnostic accuracy of gadolinium enhanced magnetic resonance angiography (Gd-MRA) of the pulmonary arteries in combination with magnetic resonance venography (MRV) of the lower extremities for the diagnosis of acute venous thromboembolic disease (VTE). The diagnostic accuracy of Gd-MRA alone and in combination with MRV will be expressed as sensitivity, specificity, and likelihood ratio for positive and negative tests. The study design is a prospective study of consecutive patients incorporating standardized inclusion/exclusion criteria, complete ascertainment of patient characteristics and outcomes, uniform diagnostic criteria, and unbiased paired central readings of imaging studies. Over a period of two years, 1256 patients with clinically suspected acute PE will be recruited at 7 clinical centers. All patients will undergo clinically indicated tests to diagnose or exclude PE and VTE. The composite reference standard for the diagnosis of acute VTE includes a high probability ventilation/perf usion (V/Q) lung scan in a patient with no prior PE, a positive contrast enhanced multidetector spiral CT of the chest or positive venous phase imaging of the lower extremities in a patient with a high or intermediate objective clinical assessment or a positive pulmonary digital subtraction angiogram (DSA). Venous thromboembolic disease will be excluded by a low D-dimer using the quantitative rapid enzyme- linked immuosorbent assay (ELISA) combined with a validated low probability clinical assessment, normal (V/Q) lung scan, negative spiral CT of the chest combined with negative venous phase imaging of the legs in a patient with a low or moderate objective clinical probability of PE, or a negative pulmonary DSA. It is expected that 314 patients will have PE or VTE and they will undergo Gd-MRA. It is expected that 942 patients will be shown to have no PE or VTE. From among this group, 314 patients will be randomly selected for the index test, Gd-MRA/MRV.